8991001997 has 2 divisors, whose sum is σ = 8991001998. Its totient is φ = 8991001996.

The previous prime is 8991001963. The next prime is 8991002011. The reversal of 8991001997 is 7991001998.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6404160676 + 2586841321 = 80026^2 + 50861^2 .

It is a cyclic number.

It is not a de Polignac number, because 8991001997 - 2⁶ = 8991001933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8991001927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4495500998 + 4495500999.

It is an arithmetic number, because the mean of its divisors is an integer number (4495500999).

Almost surely, 2^8991001997 is an apocalyptic number.

It is an amenable number.

8991001997 is a deficient number, since it is larger than the sum of its proper divisors (1).

8991001997 is an equidigital number, since it uses as much as digits as its factorization.

8991001997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 367416, while the sum is 53.

The square root of 8991001997 is about 94820.8943060547. The cubic root of 8991001997 is about 2079.3903844804.

Subtracting from 8991001997 its reverse (7991001998), we obtain a palindrome (999999999).

It can be divided in two parts, 8991001 and 997, that added together give a palindrome (8991998).

The spelling of 8991001997 in words is "eight billion, nine hundred ninety-one million, one thousand, nine hundred ninety-seven".